Polystyrene blends

ABSTRACT

A method of preparing a polystyrene blend that includes combining a first polystyrene composition having a first melt flow index with a second polystyrene composition having a second melt flow index and forming a polystyrene blend, the second melt flow index being at least 2 dg/min higher that the first melt flow index. The polystyrene blend has an observed tensile strength value greater than 3% above the expected tensile strength value. The second polystyrene composition can include a recycled polystyrene material, which can include expanded polystyrene. An alternate method of preparing the polystyrene blend includes combining a polystyrene composition with a styrene monomer to form a reaction mixture, polymerizing the reaction mixture and obtaining a polystyrene blend, where the polystyrene containing composition has a melt flow index at least 2 dg/min higher than the melt flow index of the styrene monomer after it has been polymerized.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.13/074,763 filed Mar. 29, 2011, and now U.S. Pat. No. 8,242,212, whichclaims priority to provisional patent application No. 61/319,427 filedon Mar. 31, 2010.

The present invention is generally related to polystyrene. Morespecifically, the present invention is related to improved methods ofmaking polystyrene blends.

BACKGROUND

Styrene, also known as vinyl benzene, is an aromatic compound that isproduced in industrial quantities from ethyl benzene. The most commonmethod of styrene production comprises the dehydrogenation ofethylbenzene, which produces a crude product of styrene andethylbenzene. Polystyrene is an aromatic polymer produced from thestyrene monomer. Polystyrene is a widely used polymer found ininsulation, packaging, disposable cutlery, and foam cups.

Expanded polystyrene (EPS) is well known and can be produced bycombining an expandable gas, such as CO₂, with polystyrene, such asduring the production of foamed products and can include extrudedpolystyrene (XPS). EPS can be used in applications such as insulationmaterial as the entrapped gaseous content resists the flow of heatthereby giving insulating properties. EPS can be used in applications inpackaging providing protection from impact due to the entrapped gaseouscontent. Other types of polystyrene include elastomer-reinforcedpolymers of monovinylidene aromatic compounds such as styrene,a-methylstyrene, and ring-substituted styrene that can be useful for arange of applications including food packaging, office supplies,point-of-purchase signs and displays, housewares and consumer goods,building insulation, and cosmetics packaging. Such elastomer-reinforcedpolymers are commonly referred to as impact modified or high impactpolystyrene (HIPS) while a styrene homopolymer may be referred to asgeneral-purpose polystyrene (GPPS).

Byproducts and excess amounts of polystyrene and polystyrene containingcompositions are produced during the process of molding, shaping andproducing the products containing polystyrene. These byproducts, alongwith post commercial, post consumer polystyrene products, often becomewaste that can end up in landfills or incinerators. It is desirable torecycle this material in order to prevent waste and pollution. It isalso desirable to obtain polystyrene having improved tensile propertiesin order that a lesser amount of polystyrene may be needed in a givenpolystyrene product, which can result in an overall reduction inpolystyrene waste.

SUMMARY

An embodiment of the present invention, either by itself or incombination with other embodiments, is a method of preparing apolystyrene blend that includes combining a first polystyrenecomposition having a first melt flow index with a second polystyrenecomposition having a second melt flow index and forming a polystyreneblend, the second melt flow index being at least 2 dg/min higher thatthe first melt flow index. The first polystyrene containing compositionhas a first tensile strength value and the second polystyrene containingcomposition has a second tensile strength value and the polystyreneblend has an expected tensile strength value. The expected tensilestrength value is a weighted average of the first tensile strength valueand the second tensile strength value based on the amount of the firstpolystyrene containing composition and the second polystyrene containingcomposition in the polystyrene blend. The polystyrene blend has anobserved tensile strength value greater than 3% above the expectedtensile strength value.

In an embodiment of the present invention, either by itself or incombination with other embodiments, the polystyrene blend can have asecond polystyrene composition:first polystyrene composition weightratio of from 1:99 to 1:1.

In an embodiment of the present invention, either by itself or incombination with other embodiments, the second polystyrene compositioncan include a recycled polystyrene material, which can include expandedpolystyrene.

In an embodiment of the present invention, either by itself or incombination with other embodiments, the combining of the firstpolystyrene composition with the second polystyrene composition canoccur in an apparatus selected from the group of a mixer, a compounder,and an extruder.

An embodiment of the present invention, either by itself or incombination with other embodiments, can include articles made from thepolystyrene blend.

An embodiment of the present invention, either by itself or incombination with other embodiments, is a method of preparing apolystyrene blend that includes combining a polystyrene composition witha styrene monomer to form a reaction mixture, polymerizing the reactionmixture in a polymerization reactor, and obtaining a polystyrene blend,where the polystyrene containing composition has a melt flow index atleast 2 dg/min higher than the melt flow index of the styrene monomerafter it has been polymerized.

In an embodiment of the present invention, either by itself or incombination with other embodiments, the polystyrene composition can beadded to the styrene monomer in amounts ranging from 0.1 to 50 wt. %based on the total weight of the mixture and can include recycledpolystyrene material, which can include expanded polystyrene.

An embodiment of the present invention, either by itself or incombination with other embodiments, can include articles made from thepolystyrene made by the method disclosed herein.

An embodiment of the present invention, either by itself or incombination with other embodiments, is a polystyrene blend of a firstpolystyrene having a first melt flow index and a second polystyrenehaving a second melt flow index where the second melt flow index is atleast 2 dg/min higher that the first melt flow index. The secondpolystyrene is 0.1 to 40 wt. % of the total weight of the polystyreneblend and the first polystyrene has a first physical property value andthe second polystyrene has a second physical property value and thepolystyrene blend has an expected physical property value when combined.The expected physical property value is a weighted average of the firstphysical property value and the second physical property value based onthe amount of the first polystyrene and the second polystyrene in thepolystyrene blend and the polystyrene blend has an observed physicalproperty value greater than 3% above the expected physical propertyvalue.

An embodiment of the present invention, either by itself or incombination with other embodiments, can include articles made from thepolystyrene blend.

Other possible embodiments include two or more of the above embodimentsof the invention. In an embodiment the method includes all of the aboveembodiments and the various procedures can be carried out in any order.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 illustrates a graph of tensile strength and molecular weight as afunction of melt flow index.

FIG. 2 is a graph of tensile strength at break versus the melt flowindex of DSM compounded blends.

FIG. 3 is a bar graph of Yellowness Index YI versus weight percent EPS.

FIG. 4 is a microscopic picture of particles isolated from Sample B.

FIG. 5 is another microscopic picture of particles isolated from SampleB.

FIG. 6 is a graph of solution viscosity versus Sample C concentration intoluene at 22° C.

FIG. 7 is a graph of the weight of material collected on filter versusthe total weight of solution filtered.

FIG. 8 is a graph of styrene conversion versus polymerization over time.

FIG. 9 is a graph of strength at break values versus the wt % EPS in aPS mixture in accordance with the present invention.

FIG. 10 is a graph of % elongation at break values versus the wt % EPSin a mixture in accordance with the present invention.

DETAILED DESCRIPTION

The molecular weight and polymer melt viscosity of a thermoplasticcompound typically trend as the inverse of the melt flow index (MFI). Asa general rule, most physical properties, such as tensile strength andflexural strength, of a thermoplastic are a function of the molecularweight and thus the properties can also be related to the MFI (see FIG.1). According to the present invention, the blending of a high melt flowpolystyrene with a low melt flow polystyrene can give increased tensileproperties within a given melt flow range falling between that of thehigh and low melt flow products.

It has been found that the tensile properties of polystyrene can beimproved by blending an amount of high melt flow index polystyrene withlow melt flow index polystyrene. More specifically, it has been foundthat a certain amount of high melt flow index polystyrene blended with alow melt flow index polystyrene can yield a polystyrene blend havingunexpected improvements in tensile properties.

According to an embodiment of the present invention, a polystyrene blendis obtained by combining a polystyrene composition having a high meltflow index with a polystyrene composition having a low melt flow index.In an embodiment, a polystyrene blend is obtained by combining a firstpolystyrene composition with a second polystyrene composition where thedifference in the melt flow index of the two is greater than 2 dg/min.In an embodiment, a polystyrene blend is obtained by combining apolystyrene composition having a melt flow index of greater than 7dg/min with a polystyrene composition having a melt flow index of lessthan 5 dg/min. In another embodiment, a polystyrene blend is obtained bycombining a polystyrene composition having a melt flow index of greaterthan 9 dg/min with a polystyrene composition having a melt flow index ofless than 5 dg/min. In a further embodiment, a polystyrene blend isobtained by combining a polystyrene composition having a melt flow indexof greater than 10 dg/min with a polystyrene composition having a meltflow index of less than 5 dg/min.

In an embodiment, the high melt flow polystyrene is added to thepolystyrene blend in amounts of less than 60 wt. % based on the weightof the polystyrene blend. In another embodiment, the high melt flowpolystyrene is added to the polystyrene blend in amounts ranging from0.1 to 50 wt. % based on the weight of the polystyrene blend. In afurther embodiment, the high melt flow polystyrene is added to thepolystyrene blend in amounts ranging from 1 to 40 wt. % based on theweight of the polystyrene blend.

In an embodiment, the polystyrene blend contains high melt flowpolystyrene:low melt flow polystyrene weight ratios of from 1:99 to 1:1.In another embodiment, the polystyrene blend contains high melt flowpolystyrene:low melt flow polystyrene weight ratios of from 1:50 to 2:3.In a further embodiment, the polystyrene blend contains high melt flowpolystyrene:low melt flow polystyrene weight ratios of from 1:10 to 1:2.

In an embodiment, the difference in melt flow index between the highmelt flow index polystyrene and the low melt flow index polystyrene isat least 2 dg/min. In an embodiment, the high melt flow indexpolystyrene is present in the polystyrene blend in amounts ranging from0.1 wt. % to 40 wt. % of the total weight of the combined polystyreneblend. If the difference between the high melt flow index and the lowmelt flow index is at least greater than 2 dg/min and the high melt flowindex polystyrene is present in amounts ranging from 0.1 wt. % to 40 wt.% of the total weight of the combined polystyrene blend, then certainphysical properties will be unexpectedly improved. For example, tensilestrength and percent elongation will show an unexpected improvement.

In an embodiment, a polystyrene blend is achieved by combining apolystyrene containing high melt flow GPPS. In an embodiment, apolystyrene blend is achieved by combining a polystyrene containingcompound with a recycled material. In another embodiment, a polystyreneblend is obtained by combining a polystyrene containing compound with arecycled material containing polystyrene. In a further embodiment, therecycled material includes expanded polystyrene. In a furtherembodiment, the recycled material includes post industrial PS. In afurther embodiment, the recycled material includes post commercial PS.In a further embodiment, the recycled material includes post consumerPS. In a further embodiment, the recycled material includes postconstruction PS.

In an embodiment, the polystyrene blend is obtained by combining astyrene monomer with a recycled material. In another embodiment, apolystyrene blend is obtained by combining a styrene monomer with arecycled material containing polystyrene. In a further embodiment, therecycled material includes expanded polystyrene.

Expanded polystyrene (EPS) can be used in molded sheets for buildinginsulation and packing material for cushioning fragile items insideboxes. EPS recycle includes EPS scraps and byproducts left over from themaking of products containing EPS and after their use. These recyclematerials can be classified as post industrial, post commercial, postconsumer, and post construction. Post industrial EPS primarily includesscrap from EPS molders and fabricators. Post industrial EPS is usuallythe cleanest, or less contaminated, type of recycled EPS. Postcommercial EPS primarily includes packaging materials from furniture andappliances. Post commercial EPS usually has a greater contamination thanpost industrial EPS. Post commercial recycled EPS will still containsome contaminants (e.g. wood, glue, paper, etc.); however, it should becleaner than post consumer EPS and post construction EPS. Post consumerEPS includes a wider range of products including food packaging (e.g.coffee cups, clam shells, etc.). Post construction EPS includes foammaterials generated from building renovations and demolition.

In an embodiment, the high melt flow index polystyrene composition is arecycled material. In another embodiment, the high melt flow indexpolystyrene composition is a recycled EPS. In a further embodiment, therecycled EPS is post industrial and/or post commercial EPS. Recycledmaterial can contain contamination. For instance, recycled EPS cancontain contamination due to other components in the recycle, such astape, cellulose (paper), and other plastics. If present in a polystyreneblend, these contaminants usually negatively impact the physicalproperties of the blend. By using a recycled high melt flow indexpolystyrene, having contaminants, with a low melt flow indexpolystyrene, in which the difference between the high melt flow indexand the low melt flow index is at least greater than 2 and the high meltflow index polystyrene is present in amounts ranging from 0.1 wt. % to40 wt. % of the total weight of the combined polystyrene blend, thencertain physical properties will be unexpectedly improved. Thiscontaminated blend having improved physical properties can compensate tosome degree for the negative effects of contamination, allowing for agreater use of recycled materials in polystyrene blends. In anembodiment the blend having improved physical properties can compensatefor at least 20% of the negative effects of contamination, optionally atleast 10%, optionally at least 5%. In an embodiment the blend havingimproved physical properties can compensate for a majority of thenegative effects of contamination. In an embodiment the blend havingimproved physical properties can compensate for all of the negativeeffects of contamination.

In an embodiment, the high melt flow index polystyrene composition canbe incorporated into a polystyrene blend according to any method knownin the art. In an embodiment, a polystyrene blend is obtained by mixinga high melt flow index polystyrene composition with a low melt flowindex polystyrene composition. In an embodiment, the high melt flowindex polystyrene composition is combined with the low melt flow indexpolystyrene composition in a compounder and melt blended. In anotherembodiment, the high melt flow index polystyrene composition is combinedwith the low melt flow index polystyrene composition by melt blending ina mixer. In an alternative embodiment, the high melt flow indexpolystyrene composition is combined with the low melt flow indexpolystyrene composition by melt blending in an extrusion step. Invarious examples a high melt flow index polystyrene was combined with alow melt flow index polystyrene separately in a mixer, a compounder, andan extruder. In each case, similar improvements in physical propertieswere obtained under differing types of blending.

In an embodiment, the polystyrene blend has an observed tensile strengthvalue greater than 3% above the expected tensile strength value. In anembodiment, the polystyrene blend has an observed tensile strength valuegreater than 5% above the expected tensile strength value. In anembodiment, the polystyrene blend has an observed tensile strength valuegreater than 7% above the expected tensile strength value. In anembodiment, the polystyrene blend has an observed tensile strength valuegreater than 10% above the expected tensile strength value. In anembodiment, the polystyrene blend has an observed tensile strength valuegreater than 15% above the expected tensile strength value.

In an embodiment, a high melt flow index polystyrene composition iscombined with styrene monomer prior to polymerization of the styrenemonomer to produce a polymer blend product. According to an embodimentof the present invention, a polystyrene blend is obtained by combining apolystyrene composition having a high melt flow index at least 2 dg/minhigher than the melt flow index of the styrene monomer after it has beenpolymerized and polymerizing the mixture. In an embodiment, the meltflow index of the polystyrene composition is at least 4 dg/min higherthan the melt flow index of the styrene monomer after it has beenpolymerized.

In an embodiment, a polystyrene blend is obtained by combining apolystyrene composition having a melt flow index of greater than 7dg/min with a styrene monomer having a melt flow index afterpolymerization of less than 5 dg/min. In an embodiment, a polystyreneblend is obtained by combining a polystyrene composition having a meltflow index of greater than 9 dg/min with a styrene monomer having a meltflow index after polymerization of less than 5 dg/min. In an embodiment,a polystyrene blend is obtained by combining a polystyrene compositionhaving a melt flow index of greater than 10 dg/min with a styrenemonomer having a melt flow index after polymerization of less than 5dg/min.

In an embodiment, the high melt flow polystyrene is added to thepolystyrene monomer in amounts of less than 60 wt. % based on the weightof the final polymerized polystyrene blend. In another embodiment, thehigh melt flow polystyrene is added to the polystyrene monomer inamounts ranging from 0.1 to 50 wt. % based on the weight of the finalpolymerized polystyrene blend. In a further embodiment, the high meltflow polystyrene is added to the polystyrene monomer in amounts rangingfrom 1 to 40 wt. % based on the weight of the final polymerizedpolystyrene blend.

In Example 5 (below), a high melt flow index polystyrene composition iscombined with styrene monomer in a polymerization reactor to produce apolymer blend product. In this example, an improvement in physicalproperty was observed over polystyrene product in which the high meltflow index polystyrene composition was not combined with the styrenemonomer.

EXAMPLES

The feasibility of incorporating EPS recycled materials into high heatcrystal polystyrene (HHC PS) was investigated. Melt and reactor blendswere investigated to incorporate EPS with both methods demonstratingsimilar technical feasibility and challenges. Unexpectedly, themechanical properties of the blends seem to be relatively unchanged oreven improved with up to 40-weight percent incorporation. It is expectedthat blends of high and low melt flow polystyrenes give decreasedphysical properties relative to the properties of the low melt flowvirgin polystyrene.

Seven samples of EPS from different sources were tested. These samplesserve as a comparison of the materials that might be received in arecycle facility. As shown in Table 1, the EPS will have a range ofphysical properties. While not reflected in these analyses, often timesthese samples contained adhesive and paper products (e.g. from labels)that were not always visible, but encapsulated within the densifiedblock. This also raises the concern of product consistency within thedensified blocks. Some samples are a recycled pellet of EPS material.Sample E is PS that has been treated to be fire resistant.

TABLE 1 Analyses of EPS Recycle. Sample ID A B C D E F G Form FoamDensified Densified Pellets Pellets Densified Densified Board Color PinkWhite White Amber Brown White White MFI (dg/min) 13.0 10.8 7.2 3.7 37.0NA NA Mn (g/mol) 81,758 93,347 87,925 95,014 46,008 88,590 93,593 Mw(g/mol) 215,368 249,489 233,834 255,747 115,468 317,499 280,775 Mz(g/mol) 384,281 468,934 422,811 483,468 212,302 745,552 596,481 D(Mw/Mn) 2.6 2.7 2.7 2.7 2.5 3.6 3.0 Mp (g/mol) 193,276 189,475 190,127188,270 107,563 189,209 198,169 Wt. % 0 0 0.13 0 0.94 0 0 Mineral Oil

Physical blending of the EPS recycle samples with HHC PS was donethrough melt blending using a DSM compounder, a Haake mixer, and aBrabender extruder. The HHC PS used in these studies are provided inTable 2, two of the PS grades, 535 & 523 W are commercially availablefrom Total Petrochemicals Inc., while the third PS will be referred toas GPPS and has the properties as found in Table 2. Optimized conditionswere sought to mitigate negative effects of the EPS on MFI, MW, andcolor. Those parameters are reported below. The EPS was first ground toa fine powder before mixing with virgin crystal PS pellets. Blend levelsup to 40 weight percent were targeted in the final product. Because ofthe low bulk density and very fine nature of the ground EPS, slightvariations in the targeted blend concentrations were expected. This wasdue to the challenges of delivering this material blended with pelletsto the mixing equipment. Finally, to complete polymer property testing aminimum of 150 grams of the blends were needed.

TABLE 2 HHC PS Grades Employed in These Studies. HHC PS Grade 535 GPPS523W Target MFI (dg/min) 4.0 +/− 0.5 5.0 +/− 0.7 11.0 +/− 2.0 Mn (g/mol)93,700 79,800 64,500 Mw (g/mol) 255,000 235,300 196,400 Mz (g/mol)247,100 229,400 204,800 D (Mw/Mn) 2.7 2.9 3.0 Zinc StearateConcentration 1,000 0 0 (ppm)

Example 1

The conditions employed in a DSM compounder are given in Table 3. Forthis set of experiments GPPS was blended with the Sample A EPS. Due tothe small volume of the DSM compounder, multiple eight-gram samples wereprepared in order to complete the polymer testing. The polymerproperties are provided in Table 4. Expectedly, the melt flows increasedwith EPS incorporation due to its higher MFI relative to GPPS. However,even with the addition of Irganox 1076®(octadecyl-3,5-di-tert-butyl-4-hydroxyhydrocinnamate) to stabilize thepolymer melt, the data suggest there was considerable degradation of theblend as the measured values were somewhat higher than the predictednumbers for the 10 and 20 weight percent blends. In part this was due tothe presence of brominated flame retardant, and it is likely that theDSM extruder conditions lead to considerable degradation as well. Theaddition of the lower MW EPS was unexpectedly found to provide highertensile strength relative to the HHC. The lower strength EPS, shouldhave resulted in a drop in strength in the blends. This same trend wasseen in mixtures of GPPS and 523 (FIG. 2).

TABLE 3 DSM Compounder Conditions. Barrel Temperature (° C.) 200 MixerSpeed (rpm) 30 Residence Time (minutes) 3 Irganox 1076 ® Conc. (ppm)1,000 Purge Gas Nitrogen

TABLE 4 DSM Compounder Blended GPPS and Sample A EPS Polymer Properties.% Predicted Tensile Strength Tensile Elonga- Wt. % MFI MFI Modulus atBreak at Max tion EPS (dg/min) (dg/min) (psi) (psi) (psi) at Break 03.70 3.7 466,090 6,106 6,153 1.3 10 4.20 5.7 469,663 6,294 6,358 1.4 204.76 7.1 471,251 7,184 7,248 1.6 100 13.00 13 419,503 4,371 4,397 0.8

At 10 wt % EPS the predicted strength at break is 5,684 psi. Theobserved strength at break of 6,294 psi is an increase of 10.7% overprediction. At 20 wt % the predicted strength at break is 5,405 psi. Theobserved strength at break of 7,184 psi is an increase of 32% overprediction.

Example 2

A Haake mixer was also employed to melt blend virgin HHC PS with EPS.Fifty-gram samples were made and the conditions used are provided inTable 5. Once blended, the polymers were pressed into tensile bars. Forthese experiments, EPS Sample B and EPS Sample C were blended with lowand high MFI HHC PS GPPS and 523 W, respectively.

TABLE 5 Haake Mixer Conditions. Mixer Temperature (° C.) 200 Mixer Speed(rpm) 30 Residence Time (minutes) 3 Irganox 1076 ® Conc. (ppm) 1,000Purge Gas Nitrogen

The yellowness index for the GPPS/Sample B blend is provided in FIG. 3.These numbers are not surprising as the tensile bars had a yellow-brownappearance with yellow and black contaminants. A few yellow and brownparticles isolated from the EPS were identified by infrared spectroscopyto be either polyurethane or a derivative of cellulose (FIGS. 4 and 5).Both materials can be found in tape, stickers and paper. Attempts tomitigate the color issues with 1,000 ppm Irgafos® 168 (Ciba-Tris(2,4-di-tert-butylphenyl)phosphate) instead of Irganox® 1076 were notsuccessful likely due to the fact that the color was caused primarilyfrom the contaminants already present in the EPS. The addition of ZnOonly served to whiten the polymer.

Table 6 provides the physical properties of the HHC PS and EPS blends.Like the DSM compounded samples, the melt flows trend with the blendratios of the two different melt flow polystyrenes. Additionally, thepredicted and measured melt flows are comparable, which suggests theHaake mixer conditions were more amenable to minimize degradation.Similarly to the DSM results, the percent elongation and tensilestrength rose somewhat for the low melt flow HHC PS with blends up toroughly 20 weight percent EPS. On the other hand, the tensile propertiesremain essentially unchanged throughout the blend concentrationscontaining high flow 523 and EPS Sample B.

TABLE 6 Polymer Properties of Haake Mixed Polymer Blends. PredictedTensile Wt. % MFI MFI Modulus Strength at Tensile at % Elongation BlendEPS (dg/min) (dg/min) (psi) Break (psi) Max (psi) at Break GPPS/Sample B0 4.5 4.5 462,643 6,942 7,021 1.78 5 4.8 4.4 454,164 7,505 7,550 2.20 105.0 5.3 450,817 7,369 7,417 2.11 20 5.6 5.9 451,346 7,461 7,500 2.14 406.9 6.4 448,607 6,813 6,834 1.74 100 13.0 13.0 454,032 6,323 6,358 1.52GPPS/Sample C 0 4.8 4.8 462,643 6,942 7,021 1.78 5 5.0 4.8 445,470 7,0917,165 1.93 10 5.1 5.1 448,480 7,283 7,338 2.04 20 5.5 5.8 453,298 6,8626,874 1.76 40 6.3 6.5 446,715 6,155 6,206 1.52 100 9.5 9.5 441,039 5,7445,827 1.45 523/Sample B 0 10.7 10.7 459065 6252 6302 1.47 20 10.4 11.0446314 6016 6107 1.46 40 10.2 10.2 446454 6199 6245 1.51 100 9.4 9.4441039 5744 5827 1.45

TABLE 7 Polymer Properties of GPPS/EPS Sample B Polymer Blends. StrengthPredicted Measured Difference in wt % EPS (psi) Strength (psi) Strength(psi) Strength (%) 0 6942 6942 — 5 6911 7505 8.6 10 6880 7369 7.1 206818 7461 9.4 40 6694 6813 1.8 100 6323 6323 —

For a blend of GPPS/Sample B the strength at break was predicted to bethe weighted average based on the wt % of the blend. For a blend ofGPPS/Sample B the strength at break was measured to be above theprojected strength based on the wt % of the blend. The blend componentshave a MFI (dg/min) of 4.5 for the Sample B and 13.0 for the GPPSpolystyrene. The difference of the MFI values of the components was 8.5.Between the blend range of 0.1 wt % and 40 wt % EPS the strength wasfound to be increased at points within this range above what wasexpected. This is illustrated in FIG. 9 where the strength at breakvalues are plotted versus the percent EPS in the mixture. The %elongation at break values versus percent EPS in the mixture is shown inFIG. 10. At the measured data points the difference in strength(strength at break in psi), in percent above the expected value, rangesfrom 1.8 to 9.4, as shown in Table 7. If a correlation between thedifference of the MFI values of the two components and the difference instrength in percent above the expected value is made, it can be seenthat the increase in strength in percent above the expected value canrange between 0.2 and 1.1 times the difference of the MFI values.

In embodiments of the present invention an increase in strength inpercent above the expected value can be greater than 0.2 times thedifference of the MFI values. In an embodiment the increase in strengthin percent above the expected value can range from between 0.2 and 5.0times the difference of the MFI values, optionally from between 0.2 and4.0 times the difference of the MFI values, optionally from between 0.2and 3.0 times the difference of the MFI values, optionally from between0.2 and 2.0 times the difference of the MFI values. In embodiments ofthe present invention an increase in strength in percent above theexpected value can be greater than 3%, optionally greater than 5%,optionally greater than 7%.

In embodiments of the present invention an increase in elongation atbreak in percent above the expected value can be greater than 0.2 timesthe difference of the MFI values. In an embodiment the increase inelongation at break in percent above the expected value can range frombetween 0.2 and 5.0 times the difference of the MFI values, optionallyfrom between 0.2 and 4.0 times the difference of the MFI values,optionally from between 0.2 and 3.0 times the difference of the MFIvalues, optionally from between 0.2 and 2.0 times the difference of theMFI values.

In embodiments of the present invention an increase in physicalproperties in percent above the expected value can be greater than 0.2times the difference of the MFI values. In an embodiment the increase inphysical properties in percent above the expected value can range frombetween 0.2 and 5.0 times the difference of the MFI values, optionallyfrom between 0.2 and 4.0 times the difference of the MFI values,optionally from between 0.2 and 3.0 times the difference of the MFIvalues, optionally from between 0.2 and 2.0 times the difference of theMFI values.

Example 3

A Brabender extruder was also employed to melt blend virgin HHC PS withEPS. The Brabender extrusion conditions are given in Table 8. It shouldbe noted that substantial improvements in the quality of the finalpellets were made using the Brabender extruder. However, some processissues were seen that were related to feeding mixtures of the HHC PSpellets and ground EPS. The EPS tended to separate from the pellets inthe feed hopper leading to some irregular throughput. On the other handthere were no feed issues when using pellet blends employing pellets ofSamples D & E. As shown, Irganox 1076® was not required in the Brabenderto minimize polymer degradation. Moreover, the addition of 400 ppm ofIrganox 1076® led to a notable increase in the brown tint of thepellets. Changing the screen pack from 200 to 60 mesh did lead to aslight increase in the yellowness of the pellets, a rise in the yellowand black speck contamination, and a drop in the initial back pressure(1,600 to 800 psi). Even with a 60 mesh size, the densified materialsresulted in faster screen pack blinding, while the EPS in pellet formgave little change in the pressure with similar throughputs.

TABLE 8 Brabender Extrusion Conditions. Zone Temperatures (° C.) 200Screw Speed (rpm) 100 Screen Pack (mesh) 60 Optical Brightner (ppm) 0,30 Nitrogen Purge On

Table 9 provides polymer data using the optimized conditions given inTable 8. As shown, the predicted and measured melt flows are similar foreach sample. This suggests the Brabender extruder provided sufficientmixing without leading to vis breaking of the polymer. An opticalbrightener Ciba® UVITEX®OB-2,5-thiophenediylbis(5-tert-butyl-1,3-benzoxazole) (30 ppm) was usedfor blends containing Sample C and it is not surprising that lowerhunter color numbers were seen when compared to the Sample F & G EPSblends made without this additive. The blended polymers of Sample D $ Epellets have relatively good color values even in the absence of anyoptical brightener. Finally, similar trends to those reported for theDSM and Haake experiments are seen in the tensile properties reportedbelow. For the low melt flow WIC PS grades blended with high flow EPSproducts, there looks to be an increase in the tensile strength withblends containing up to 20-weight percent EPS. For the higher melt flowPS blended with high melt flow EPS, there is little change in thetensile strength.

TABLE 9 Polymer Properties of Brabender Extruded HHC PS/EPS Blends.Predicted Tensile Strength Tensile % Wt. % MFI MFI Modulus at Break atMax Elongation Hunter Color Blend EPS (dg/min) (dg/min) (psi) (psi)(psi) at Break L b YI 535/Sample C 0 4.5 4.5 448,696 7,219 7,265 1.8480.31 −0.02 −0.5 20 5.7 5.4 447,881 7,524 7,524 1.93 80.3 −1.36 −2.51 406.2 6.4 442,584 6,980 7,025 1.77 80.34 1.14 2.56 523/Sample C 0 12.612.6 449,625 5,896 5,966 1.38 81.99 1.01 1.13 20 12.1 11.9 443,790 5,9585,991 1.40 81.82 −0.8 −1.51 40 11.8 11.6 441,735 5,281 5,318 1.23 80.611.1 2.06 535/Sample D 0 4.6 4.6 448,696 6,019 6,082 1.42 80.31 −0.02−0.5 20 4.6 4.6 449,840 5,971 5,957 1.42 81.47 0.62 0.49 40 4.5 4.5446,367 6,339 6,386 1.55 81.45 1.47 2.1 100 4.4 4.4 450,701 6,714 6,7301.67 81.47 3.86 6.5 523/Sample D 0 11.5 11.5 449,625 5,294 5,366 1.1681.99 1.01 1.13 20 9.1 9.5 451,256 5,184 5,285 1.27 81.54 0.83 0.79 407.6 7.8 451,473 6,180 6,202 1.48 81.4 1.38 2.19 100 4.4 4.4 450,7016,714 6,730 1.67 81.47 3.86 6.5 535/Sample F 0 4.6 4.6 448,696 6,0196,082 1.42 80.31 −0.02 −0.5 20 5.3 5.1 451,338 6,529 6,547 1.59 78.782.14 4 40 5.8 5.6 449,540 6,439 6,480 1.59 76.99 4.85 10.13 100 7.4 7.4443,484 6,415 6,474 1.80 69.17 11.25 27.61 523/Sample F 0 11.5 11.5449,625 5,294 5,366 1.16 81.99 1.01 1.13 20 10.4 10.5 442,076 5,3325,387 1.26 79.56 2.58 4.89 40 9.5 9.6 442,061 5,419 5,430 1.30 77.4 4.499.17 100 7.4 7.4 443,484 6,415 6,474 1.80 69.17 11.25 27.61

Example 4

The incorporation of recycled EPS via reactor blending involveddissolving the EPS in styrene monomer and then completing batchpolymerizations. Solution viscosities were measured using a BrookfieldViscometer to determine the maximum concentration of EPS that could befed to the reactor (FIG. 6). For reference, solution viscosities of 535and 523 are included. As shown, the viscosities remain essentiallyunchanged up to 20-weight percent PS. They rise rapidly after this andreach ca. 6,000 cP at 40-weight percent EPS. It should also be notedthat introducing greater than 20-weight percent EPS proved difficult asthe thicker solutions reduced the wetting of the flakes giving longdissolution times.

In order to remove contaminants from the EPS solution, filtrations usingdifferent size filters were completed. As shown in FIG. 7, the smallermicron filters plug at a quicker rate than the 20-micron filter asindicated by the sudden gain in mass on the filters. This suggests thatmost aromatic insoluble materials have particle sizes between 10 and 20microns. This method can also be used to estimate the rate at whichfilters will plug or to estimate the size filters required to removeinsoluble contaminants.

The polymerization experiments were conducted in a 0.5 liter reactorkettle equipped with a flat blade paddle under conditions as provided inTable 10. With a 20-weight percent EPS containing feed, the final EPScontent at 70-percent solids was estimated to be 28.5 weight percent. Asshown in FIG. 8, the slopes appear similar for each batch suggestingpolymerization rates are unaffected by the EPS recycle. Interestingly, asimilar trend to that seen for the melt blended materials was shown forthe tensile properties of the batches, where the tensile strength andpercent elongation increased with the addition of higher melt flow EPS(Table 11). Finally, the use of blue dye, Macrolex violet B from LanxessAG, tended to mitigate any color problems, but at very highconcentrations (Table 12).

TABLE 10 Batch Polymerization Conditions. Polymerization Temperature (°C.) 130 EPS Sample B Feed Concentration (Wt. %) 0, 20 Agitation Rate(rpm) 150 Ethylbenzene Concentration (Wt. %) 10 L-233 Concentration(ppm) 177 Blue Dye Feed Concentration (ppb) 0, 50, 150 Target Solids(Wt. %) 70 Devol Temperature (° C.) 240 Devol Pressure (torr) <10 DevolTime (minutes) 45

TABLE 11 Polymer Properties for Batch Polymers. % Predicted TensileStrength Tensile Elonga- Wt. % MFI MFI Modulus at Break at Max tion EPS(dg/min) (dg/min) (psi) (psi) (psi) at Break 0 NA 5.0 451,039 6,4816,536 1.59 28.5 6.2 6.4 447,598 6,875 6,905 1.74

TABLE 12 Hunter Color Data for Batch Polymers. Blue Dye Wt. % EPSConcentration (ppb) L a b YI 0 0 79.83 −1.8 2.19 3.29 28.5 0 78.39 −1.164.11 8.31 28.5 50 78.21 −0.99 3.45 6.98 28.5 150 76.18 −1.55 2.21 5.05

Example 5

Table 13 shows the tensile properties of DSM melt blended samples ofvirgin GPPS (MFI=4.8 dg/min) and 523 W (MFI=10.4). Unexpectedly, theblends having melt flows of 5.6 and 6.5 show increases in tensile atbreak by as much as 20 percent of the predicted value from the equationshown in FIG. 1. Along those same lines, the percent elongation at breakrises for the physical blends as well.

TABLE 13 DSM Compounder Blended GPPS and 523 W. Tensile Tensile % MFITensile at at Elonga- Wt. % (dg/ Modulus Break Max tion Blend 523 W min)(psi) (psi) (psi) at Break GPPS 0 4.8 462643 6942 7021 1.8 GPPS/523 W 205.6 480773 7448 7549 2.0 GPPS/523 W 20 5.6 445420 7052 7087 1.9 GPPS/523W 40 7.9 450840 6471 6525 1.6 GPPS/523 W 40 6.5 449840 7860 7904 2.3 523W 100 10.4 459065 6252 6302 1.5

As used herein, the term “polystyrene composition” includes anypolystyrene containing composition.

ASTM tests for measurements include: MFI—ASTM 1238 (200° C./5 kg); MW byGPC—ASTM 5296-05; YI—ASTM E313; Tensile Strength—ASTM D638; FlexStrength—ASTM D790.

Other possible embodiments include two or more of the above embodimentsof the invention. In an embodiment the method includes all of the aboveembodiments and the various procedures can be carried out in any order.

It is to be understood that while illustrative embodiments have beendepicted and described, modifications thereof can be made by one skilledin the art without departing from the spirit and scope of thedisclosure. Where numerical ranges or limitations are expressly stated,such express ranges or limitations should be understood to includeiterative ranges or limitations of like magnitude falling within theexpressly stated ranges or limitations (e.g., from about 1 to about 10includes, 2, 3, 4, etc.; greater than 0.10 includes 0.11, 0.12, 0.13,etc.).

Use of the term “optionally” with respect to any element of a claim isintended to mean that the subject element is required, or alternatively,is not required. Both alternatives are intended to be within the scopeof the claim. Use of broader terms such as comprises, includes, having,etc. should be understood to provide support for narrower terms such asconsisting of, consisting essentially of, comprised substantially of,etc.

Depending on the context, all references herein to the “invention” mayin some cases refer to certain specific embodiments only. In other casesit may refer to subject matter recited in one or more, but notnecessarily all, of the claims. While the foregoing is directed toembodiments, versions and examples of the present invention, which areincluded to enable a person of ordinary skill in the art to make and usethe inventions when the information in this patent is combined withavailable information and technology, the inventions are not limited toonly these particular embodiments, versions and examples. Also, it iswithin the scope of this disclosure that the aspects and embodimentsdisclosed herein are usable and combinable with every other embodimentand/or aspect disclosed herein, and consequently, this disclosure isenabling for any and all combinations of the embodiments and/or aspectsdisclosed herein, Other and further embodiments, versions and examplesof the invention may be devised without departing from the basic scopethereof and the scope thereof is determined by the claims that follow.

1. A polystyrene blend, comprising: a first polystyrene containingcomposition having a first melt flow index; and a second polystyrenecontaining composition having a second melt flow index; wherein thesecond melt flow index is at least 2 dg/min higher that the first meltflow index; wherein the second polystyrene containing compositioncomprises 0.1 to 40 wt. % of the total weight of the polystyrene blend;wherein the first polystyrene containing composition has a firstphysical property value and the second polystyrene containingcomposition has a second physical property value and the polystyreneblend has an expected physical property value; wherein the expectedphysical property value is a weighted average of the first physicalproperty value and the second physical property value based on theamount of the first polystyrene containing composition and the secondpolystyrene containing composition in the polystyrene blend; and whereinthe polystyrene blend has an observed physical property value greaterthan 3% above the expected physical property value.
 2. The polystyreneblend of claim 1, wherein the physical property is tensile strength. 3.The polystyrene blend of claim 1, wherein the physical property is %elongation at break.
 4. The polystyrene blend of claim 1, wherein thesecond polystyrene containing composition is a recycled material.
 5. Thepolystyrene blend of claim 4, wherein the recycled material comprisesexpanded polystyrene.
 6. An article made from the polystyrene blend ofclaim 1.